Goodwill and Intangible Assets - Other Intangibles Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017	Jul. 31, 2017
Other Intangible Assets [Line Items]
Gross Carrying Amount	$ 89,637		$ 89,637		$ 89,685
Accumulated Amortization	(41,601)		(41,601)		(36,609)
Net Book Value	48,036		48,036		$ 53,076
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Intangible Assets	1,620	$ 1,766	4,930	$ 5,349
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	6,513		6,513
Finite-Lived Intangible Assets, Amortization Expense, Year Two	6,174		6,174
Finite-Lived Intangible Assets, Amortization Expense, Year Three	5,210		5,210
Finite-Lived Intangible Assets, Amortization Expense, Year Four	5,168		5,168
Finite-Lived Intangible Assets, Amortization Expense, Year Five	5,014		$ 5,014
Patents [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	1,448		$ 1,448		$ 1,358
Accumulated Amortization	(816)		(816)		(471)
Net Book Value	632		$ 632		$ 887
Trademarks And Other [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			9 years		9 years
Gross Carrying Amount	4,593		$ 4,593		$ 4,528
Accumulated Amortization	(4,449)		(4,449)		(4,229)
Net Book Value	144		$ 144		$ 299
Customer relationships [Member]
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			8 years		8 years
Gross Carrying Amount	60,742		$ 60,742		$ 60,759
Accumulated Amortization	(36,336)		(36,336)		(31,909)
Net Book Value	24,406		24,406		28,850
Trademarks [Member]
Other Intangible Assets [Line Items]
Gross Carrying Amount	22,854		22,854		23,040
Accumulated Amortization	0		0		0
Net Book Value	$ 22,854		$ 22,854		$ 23,040